Cough,
I agree with your explanation re a situation such as LAM holding with STN/LTN available from that point.
It isn’t the same logic for everywhere however. Destination LGW, and holding south of the field with LHR fuel alternate, there IS a point when eating into reserve fuel that the decision IS to commit to LGW with circumstances/information available suitably considered. A required diversion post that decision would require an emergency declaration as having used already some of the diversion fuel in holding and therefore now planning to enter into my minimum final fuel.
In short there may be alternatives as you suggest depending on geographical location and other airports close by from that hold vs the airfield itself. Sometimes however there may not be.
Rgds
30W